Valentine's Day—when people's hearts race in anticipation and hope! OK, maybe not everyone has a racing heart today, but there are certainly some animals that do. Every minute a human heart might beat a comfortable 72 times—or maybe even 150 when that person is frightened or doing a strenuous activity.
Do larger animals need a faster heart rate? Surprise! It is actually
just the opposite! A black bear's heart may only beat 40 to 50 times per minute,
but a shrew's heart can beat 800 times. A hummingbird's heart rate can be 1200
beats per minute! No wonder they require so much energy and are so fast! Birds also
have high blood pressure. You may have joked about being "scared to death",
but for a bird, this is no joke! Give it too big a surprise, and its heart can actually
rupture! 
Remember, don't
break any hearts today.
Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.
Contributor: Kodi Jeffery, formerly of the Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Anna's Hummingbird. Photograph by Lloyd Glenn Ingles. © California Academy of Sciences.
Welty, J. C. 1982. The Life of Birds. Saunders College Publishing, 3rd ed., Philadelphia, 754 pp. See pp. 6, 132.
Heart Rates of various animals (scroll down to Lesson 25).